Revisiting the age, evolutionary history and species level diversity of the genus Hydra (Cnidaria: Hydrozoa)

Two-step evolution of endosymbiosis between hydra and algae

“…Evolution of endosymbiotic potential occurred more recently in H. vulgaris group than H. viridissima group Schwentner and Bosch (2015) Our phylogenetic analysis showed that the H. vulgaris group strains were grouped into three clusters, and cluster α diverged first, followed by β and γ. Among the clusters, only cluster γ strains have endosymbiotic potential.…”

“…The support for internal branches was evaluated using bootstrap percentages from 1,000 nonparametric replicates for the ML method and using Bayesian posterior probabilities for the BI. The divergence time between H. oligactis group and H. vulgaris group (72-132 million years ago, Mya) that was estimated by Schwentner and Bosch (2015) was used to calibrate the estimated times of divergence of the clusters. The analysis was conducted using the RelTime method (Tamura et al, 2012).…”

“…Therefore, the current endosymbiotic Chlorococcum in J7 may not show endosymbiosis with the α and β lineages. However, it has been shown that in the H. viridissima group, an aposymbiotic strain can harbor a symbiont from a different strain even though the divergence time between the strains was estimated to be 77-152 Mya (Schwentner and Bosch, 2015). If this time scale is applied to the H. vulgaris group, it is unlikely that the H. vulgaris group would have experienced such changes in host specificity among strains.…”

“…Phylogenetic studies of the genus Hydra have shown that the species can be classified into four monophyletic groups, namely, H. vulgaris group, H. oligactis group, H. braueri group, and H. viridissima group (Kawaida et al, 2010;Martínez et al, 2010, Schwentner andBosch, 2015). One of the primary characteristics of the H. viridissima group is endosymbiosis with the alga Chlorella (Dunn, 1987;McAuley, 1986).…”

Description and Phylogenetic Characterization of Hydra from Naukuchiatal (Uttarakhand, India) and Comparison with other <i>Hydra</i> Strains

“…Later, the genus Hydra was divided into four different groups: oligactis (stalked hydra), vulgaris (common hydra), braueri (gracile hydra) and viridissima (green hydra), based on both morphological differences 3 and molecular phylogenetic analysis 4 . However, the field of hydra taxonomy is believed to be an actively evolving field and much remains to be done 5 . This needs continued inputs from all over the globe.…”